During the forthcoming year we plan to continue our studies to elucidate the properties of the MDCK cells. 1) We are studying the relationship between (a) growth, (b) Na ion transport, (c) the A-amino acid transport system activity and (d) synthesis of polyamines. 2) We are studying the properties of the furosemide-sensitive NaCl/KCl transport system in MDCK cells using genetic and biochemical techniques. 3) We are studying the dependencies of the activities of the amiloride-sensitive and the furosemide-sensitive Na ion transport systems on the hormonal composition of the medium in serum free solution. 4) We plan to attempt solubilization and reconstitution of the amiloride sensitive transport system in phospholipid lyposomes as a prelude to in vitro assay.